MODULATION OF THE EXPRESSION OF HLA CLASS II ANTIGENS BY GAMMA INTERFERON AND PHORBOL ESTER TPA ON MYELOID LEUKAEMIC CELL LINES

SUMMARY We investigated the effect of gamma interferon and phorbol ester (TPA), on the expression of HLA class II molecules of myeloid leukaemic cell lines K562, U937, KG‐1, HG60 and ML‐2. Gamma interferon induced the expression of HLA‐DR but not HLA‐DQ on HL‐60 and ML‐2, increased the expression of HLA‐DR and DQ on U937 and induced the expression of HLA‐DQ on KG‐1. TPA treatment did not affect the expression of HLA class II antigens on U937 and KG‐I and induced the expression of HLA‐DR and HLA‐DQ on HL‐60 and ML‐2. TPA treatment did not affect the HLA phenotype of K562 but gamma interferon did induce HLA class I molecules. Thus, gamma interferon cannot only increase the expression of HLA products already expressed on the cells but can also induce the de novo synthesis of these molecules on myeloid leukaemic cell lines.